Sleep Less, Eat More?

Numerous studies have found a link between obesity and a lack of sleep, with both having risen dramatically in the past decades. But it’s not known whether short sleep actually causes obesity, and if it does, how?

Previous studies found that after only four hours of sleep, people tend to eat more calories the following day compared to after having a good night’s rest. Women seemed especially prone to overeating after limited sleep, consuming more than 300 extra calories than when well-rested. Areas of the brain related to food stimuli also seem activated by lack of sleep.

A new Columbia University study, published in the journal SLEEP, found that changes in levels of hunger-regulating hormones related to short sleep may be the cause of weight gain, and are different in men and women. Short sleep increased total levels of a hormone that increases appetite in men, but decreases a hormone that leads to reduced feelings of fullness in women. This is the first time such gender differences have been reported.

Columbia researchers tracked the effect of sleep duration on glucose metabolism and hormonal regulation of appetite in 27 normal weight, 30-45 year old men and women who habitually slept 7-9 hours per night.

Participants were observed under two sleep conditions. The first only slept four hours, and the second slept 7-9 hours. Napping wasn’t permitted. A controlled diet was provided during each study period.

After the first five-night study period, a two-week break allowed the short-sleep group to return to normalized sleep patterns, then the study groups swapped sleep cycles. Blood was drawn from study participants and analyzed for a number of food-intake regulating and glucose-metabolizing hormones.

Some of the key hormones targeted by the Columbia researchers included insulin, which affects the uptake of glucose into cells; leptin, which is made primarily in the fat cells and induces a feeling of fullness or satiety; gherlin, produced in the GI tract, considered the counterpart to leptin and a trigger for hunger; and GLP-1, which is made in the GI tract, stimulates insulin production, and inhibits gastric motility, contributing to a feeling of fullness.

Results showed that restricting sleep in healthy, normal weight participants had limited effect on glucose metabolism. However, short sleep increased total gherlin levels in men, but not women, and stimulated male appetite. On the other hand, women experienced reduced levels of GLP-1 and reduced feelings of fullness. Both of these hormonal changes could lead to overeating in response.

Weight gain is associated with multiple factors. We now know that limited duration of sleep contributes to obesity through hormonal effects and that regular sleep patterns of 7-9 hours create the best conditions for maintaining a healthy weight. Women should be especially vigilant with their diet when they’re short on sleep.